1. Field of the Invention
The present invention relates to a method of curing a color filter for an electronic display using an electron beam at low temperature. The present invention relates to a technique that employs an electron beam for curing a color filter at low temperature instead of curing the color filter by thermal-heating as in the prior art.
2. Description of the Related Art
A color filter module is mainly used in the field of thin film transistor liquid crystal displays (TFT-LCDs) and plasma display panels (PDPs), and is also applied to white organic light emitting diodes (OLEDs) that include a color filter.
In LCDs, PDPs or OLEDs, the color filter is generally produced by forming a black matrix pattern on a glass substrate and forming patterns of red, green and blue colors on the black matrix pattern.
Meanwhile, flexible displays have been actively studied in recent years as a next generation display technology. For the flexible display, since it is a key point to secure flexibility of the display, the glass substrate cannot be used and must be replaced with a plastic substrate. However, the plastic substrate is very vulnerable to heat, and provides many restrictions in fabrication of the color filter.
FIG. 1 is a flowchart of a conventional method of fabricating a color filter.
Referring to FIG. 1, a substrate is cleaned in S10. Here, cleaning is performed by ultraviolet irradiation, ozone, plasma or acid.
Next, a black matrix resin or color resist is coated on the substrate in S20. Here, coating is performed by spin coating or slit coating.
Then, the black matrix resin or color resist is dried in S30, followed by bead removal in S40.
Then, the entirety of the substrate is preheated in S50. At this time, the substrate is preheated to 30˜90° C.
Then, exposure and development processes are performed in S60 and S70. Here, the development process in S70 is performed at room temperature.
Then, the entirety of the substrate is cleaned in deionized water in S80.
Next, a black matrix resin or color resist pattern formed in the exposure and development processes in S60 and S70 is dried in S90, followed by curing in S95.
Typically, the color filter refers to a module that has a black matrix pattern and patterns of red, green and blue colors coated together on a substrate. Accordingly, the color filter is obtained by repeating an operating cycle from the substrate cleaning process in S10 to the curing process in S95 to sequentially form the black matrix resin pattern, the red pattern, the green pattern, and the blue pattern as described above.
FIGS. 2a to 2e are cross-sectional views illustrating the conventional method of fabricating the color filter.
Referring to FIG. 2a, a substrate 15 for a color filter is cleaned. Here, the substrate can be a glass substrate or plastic substrate, and is cleaned by ultraviolet irradiation or ozone.
Referring to FIG. 2b, a black matrix pattern 25 is formed on the substrate 15. Here, patterning the substrate is performed according to the operating cycle as described in FIG. 1.
Referring to FIG. 2c, a red pattern 35 is formed and cured on the black matrix pattern 25 and the substrate 15.
Referring to FIG. 2d, a green pattern 45 is formed and cured on the black matrix pattern 25 and the substrate 15.
Referring to FIG. 2e, a blue pattern 55 is formed and cured on the black matrix pattern 25 and the substrate 15.
Here, a process of curing a color filter for LCDs or OLEDs, that is, a baking process, is generally performed by thermal-heating in an electric oven or by ultraviolet irradiation.
Currently, when forming the color filter on the glass substrate, thermal curing is performed at about 200° C., and thus can be performed in the electric oven without any problem.
However, the plastic substrate requires a continuous temperature of 100° C. or less.
As described in FIG. 1 or FIGS. 2 to 2e, since the substrate is heated at about 200° C., the plastic substrate is deformed due limitations in terms of physical and mechanical properties, thereby making it difficult to achieve dimension control of the color filter module and precision of a fine pattern.
Furthermore, the curing process using ultraviolet rays and heat requires additives such as a photo-initiator in addition to a binder resin and a cross-linkable monomer for forming the color patterns, thereby deteriorating production efficiency.
FIG. 3 is a diagram illustrating synthesis of polymer materials constituting a color filter according to a conventional technique.
Referring to FIG. 3, a photo-initiator 3 is added to a binder resin 1, a cross-linkable monomer 5, and other additives 7. Herein, the photo-initiator refers to a material that generates radicals by UV and heat during an exposure process, and causes polymerization of the cross-linkable monomer 5 to form a polymer material 9 constituting a color filter. Thus, it is necessary to have a process of controlling the added amount of photo-initiator, which can cause deterioration of the production efficiency.
As described above, when UV or heat is used for the curing process in fabrication of the color filter on the plastic substrate for flexible displays, the limits in terms of physical and mechanical properties of the plastic substrate cause deformation of the plastic substrate, and make it difficult to control the dimensions of the color filter module and to achieve precision of a fine pattern. Furthermore, the photo-initiator must be used to achieve UV or thermal polymerization, thereby deteriorating production efficiency.